The invention relates to a device for continuously measuring the liquid level in a container, particularly in fuel container of a motor vehicle, by means of a capacitive sensor which is an oscillation-determining element of an oscillator whose output is connected to a controlling and/or indicating stage.
Devices for continuously measuring the liquid level in a container are known which contain a float and a resistance element contolled thereby whose variable part is positioned in an indicating circuit. Such devices present the disadvantage that their field of application is limited to certain container shapes and that in irregularly shaped containers they have a non-linear characteristic, which is undesirable in many cases. Moreover, their weight is relatively heavy and their structural volume large.
Furthermore, measuring devices are known that contain a capacitive sensor with two parallel electrodes, insulated from each other and from the measuring liquid, which sensor is an oscillation-determining element of an oscillator. The frequency change of the oscillator, based on the change of capacity, is indicated in an indicating stage. These devices, to be sure, can be employed much more extensively than the resistance element type described above, but they operate satisfactorily only when the relative dielectric constant of the liquid to be measured is relatively large, as is the case for example, in water.